A woman hijacked a taxi at gunpoint Tuesday in downtown Palm Springs, leading California Highway Patrol officers on a 30-mile chase that ended in an hours-long standoff on Interstate 10 in Rialto, closing the freeway and tying up rush-hour traffic for miles in both directions, authorities said.

With the taxi stopped in the westbound lanes of the freeway, the unidentified woman demanded to speak with Los Angeles County Dist. Atty. Gil Garcetti, said Officer Rod Strate of the CHP's Inland Division. "We're assuming they're out of gas due to the fact that she's demanding gas," Strate added.

CHP officers and the SWAT team of the Rialto Police Department surrounded the stranded taxi with guns drawn as television cameras broadcast the scene to Southland viewers. One group of officers approached the cab from the highway center divider holding what appeared to be bulletproof shields.

Shortly after 10 p.m., four hours into the standoff, the hostage taxi driver jumped from the front seat of the cab and ran for cover as the SWAT team detonated a "flash-bang" device to distract the woman. The hostage was unharmed, police said.

"On his own, [the cabdriver] bolted from the vehicle," said Capt. Timm Browne of the Rialto Police Department. The woman remained in the vehicle and the standoff continued.

At one point, eastbound traffic on the heavily traveled artery, the main route to the Inland Empire and Palm Springs, was backed up 10 miles, the CHP said. Westbound traffic was backed up five miles.

Officials said the woman got into the cab in Palm Springs about 4:45 p.m. and placed a gun to the head of the Romanian immigrant driver and demanded to be taken to Los Angeles. Browne told reporters the woman said she was frustrated because the district attorney's office had failed to locate her mother, a missing person in Los Angeles.

A spokeswoman for Garcetti said the district attorney contacted Rialto police and offered to help. The spokeswoman declined further comment.

Witnesses who saw the woman holding a gun to the driver called authorities, said CHP spokesman Kevin Martin. CHP patrol officers spotted the cab about 5 p.m. on Interstate 10 at Banning, about 15 miles west of Palm Springs.

Colleagues of the cabdriver, who worked out of Cathedral City, said he contacted a fellow immigrant cabdriver and described his plight in Romanian. The second driver then contacted authorities.

As the yellow taxi traveled west at 50 to 75 mph, CHP officers gave chase another 25 miles to Rialto, where the cab came to a stop at 5:30 p.m. in the freeway's center lanes.

"Time is on our side," Capt. Browne said as the standoff stretched past 10 p.m. The Rialto Police Department hostage negotiation team attempted to toss a telephone to the woman, but she was unwilling to pick it up, Browne said.

Television images appeared to show the driver smoking a cigarette as the standoff continued. The passenger rolled down the back seat window and seemed to speak to negotiators. Helicopters were asked to pull back from the scene because their noise was making it difficult to communicate with the woman.